Question

Choose the correct alkynes which gives alkanal on hydroboration and hydrolysis?
A. $C{H_3} - C \equiv C - C{H_3}$
B. $C{H_3} - C{H_2} - CH = CH - C \equiv C$
C. $C{H_3} - C \equiv CH$
D. $C{H_3} - C{H_2} - C \equiv C - C{H_3}$

Answer 1

Hint: Alkanals or aldehyde, are any of a class of organic compounds, in which a carbon atom shares a double bond with an oxygen atom, a single bond with a hydrogen atom, and a single bond with another atom or group of atoms.

Step by step solution:
First we must understand what is hydroboration and hydrolysis:
Hydroboration is the process wherein the hydrogen boron bond is added to a double bond between either carbon and carbon or carbon and nitrogen. It can also be performed on a carbon-carbon triple bond.
And in very simple words hydrolysis is a chemical process in which a molecule of water is added to a substance.
In option (A) $C{H_3} - C \equiv C - C{H_3}$
It is an internal alkyne.
It gives alkanone or ketone $C{H_3} - C{H_2} - CO - C{H_3}$ on hydroboration and hydrolysis.
In option (B) $C{H_3} - C{H_2} - CH = CH - C \equiv C$
It is a terminal alkyne.
But it will give alkenal $C{H_3} - C{H_2} - CH = CH - C{H_2}CHO$ on hydroboration and hydrolysis.
In option (D) $C{H_3} - C{H_2} - C \equiv C - C{H_3}$
It is also an internal alkyne.
It gives alkanone or ketone $C{H_3} - C{H_2} - CO - C{H_3}$ on hydroboration and hydrolysis
In option (C)
Terminal Alkynes $C{H_3} - C \equiv CH$ gives alkanal $\left( {C{H_3} - C{H_2} - CHO} \right)$on hydroboration and hydrolysis as:
$C{H_3} - C \equiv CH\xrightarrow[{hydrolysis}]{{hydroboration}}C{H_3} - CH = CHOH\xrightarrow{{ketoenoltautomerism}}C{H_3} - C{H_2} - CHO$

Hence option (C) can be considered as the correct option.

Note:
1. Alkanals are organic molecules containing only carbon (C), hydrogen (H) and oxygen (O) atoms.
2. Alkanals belong to the group of organic compounds known as aldehydes.
3. Aldehydes contain a \[C = O\] carbonyl(1), functional group.
4. A straight-chain alkanal consists of a chain of 1 or more carbon atoms joined to each other by single covalent bonds, with a \[C = O\] functional group attached to the terminal (end) carbon atom in the chain of carbon atoms.